1. Field of the Invention
The present invention relates to turbomachinerys, and for example, to a turbomachinery suitable for preventing unstable vibration of a rotor rotating at high speed.
2. Description of the Related Art
Turbomachinerys include a rotor with a rotating blade, and a stator for retaining the rotor and forming a flow path. A clearance exists between the stator and the rotor, and a labyrinth seal of a comb structure is usually used to reduce fluid leakage from the clearance.
High-speed rotation of the rotor may result in unstable vibration thereof due to the possible swirling flow of the fluid at grooves formed between the comb teeth of the labyrinth seal. To prevent unstable vibration, it is effective to reduce the swirling velocity of the fluid at the grooves. For example, as disclosed in FIG. 1 of JP-10-61407-A, a structure has been proposed that includes a guide vane set up at the fluid inlet side of a labyrinth seal in order to reduce a swirling fluid velocity.
An event of oil whip due to the swirling flow of a lubricating oil on fluid-film bearings possibly takes place as an event similar to the unstable vibration mentioned above. It is known that oil whip easily occurs with cylindrical bearings and that the occurrence of unstable vibration can be suppressed by adopting elliptical bearings or multi-robe bearings.